Mitsubishi problems

[Swedish AC]

Hi there, im new here but i will appreciate any help over here in Sweden. I have just got a M series MSZ GA25VA inverter. The technicians have been here 3 times and still i have problems. They found a leak, and refilled the system but it seems to be very low cooling. The AUTO mode is very poor and will not cope with high changes in temp, we have installed this unit in the conservatory and the unit cant cope or is there a problem that i can look for? The company who installed are new to this system so im getting no where fast.

Any help would be so helpful

[rbartlett]

the system should have been evacuated and fresh refrigerant weighed in. this should have been done after each leak.

measure the inlet air temperature and the outlet air of the indoor unit.

post these temps and we can have another think

cheers

richard

[techguy]

hi
Mitsu units only change over every 15 mins in the auto mode.That is the return air temp.has to go outside its dead band for 15 mins before a mode change occurs. Set the unit to either cooling or heating as necessary and check the return air and supply air temps you should be getting around 14 c accross the coil. Providing you are 3 degrees c off your set point. If you are closer the inverter will ramp down and as a result the temp difference will decrease. If the unit is still short of gas the inverter will ramp down to try to keep the discharge temp down. If your not getting 14 degrees c. across the coil your either short of gas or undersized.

[botrous]

I sent you a manual have a read...
I couldn't send it the way that everyone can see it but simply because I don't know how...my magic doesn't work on
computers only on fridges..

Man it would be great if you can send it to me , my email is :
pja149@hotmail.com , alternate email : send2pierre@hotmail.com
I would be more than greatful for that

[Stuart]

the system should have been evacuated and fresh refrigerant weighed in. this should have been done after each leak.

measure the inlet air temperature and the outlet air of the indoor unit.

post these temps and we can have another think

cheers

richard

Richard is right of course.

The Mitsi's use 410a gas which runs at higher pressure than the alternatives of 407c & 22.

Because of these higher pressures thicker pipework is required when the diameter is above 1/2". A larger flare is required & a specialised set of tools are also needed.

I may be wrong and doing the installers a disservice but they poss have not had much experience in the way of this new gas(410a), if they are new to Mitubishi then that may well be the case.

One hopes that when they noticed the service port was larger then they would have clicked to read the specifications.

One also hopes that when they re-charged the system they used R410A not R407c or R22

In an ideal world you would be able to check with the instalers on these details AND get a truthfull answer.

But I'll wager that would not be the answer you recieve.

[Peter_1]

I can be wrong but aren't both lines between indoor and outdoor units both low pressure lines?

[rbartlett]

I can be wrong but aren't both lines between indoor and outdoor units both low pressure lines?

not when it's in heat mode and the indoor filters not been cleaned for months

cheers

richard

[Peter_1]

Ooopss, you're right Richard.

[Swedish AC]

Thanks everyone for the helpful info. We still await our installation engs return. They have been in contact with Mitsu Sweden and we will see what happens. Thet did use 410 to recharge the system, not sure if they just topped it up tho or completly refilled. The pressures on the lines were as follows, 33bar on the heating and 10bar on the cooling, i wrote these down but have no idea if this is good or bad, maybe some one will know. He did use a laser heat gauge on the outlet and this temp reading was around 4 degrees, which he said was ok but its the volume of air that seems to be low to me, like the system is "choked", the filters are new and clean but i read that the size of pipe may affect this also or have i misunderstood this? What size should they be for this unit please? They look to be in the region of 8 or 10mm at the outside unit!!!


Thanks for all the help its most appreciated over here.

[Peter_1]

If the installation is new and was done by the official importer of Mitsubishi, all should be done under warranty of the techs who installed these units, so why worry before.
Same for the pipe sizes, that's their problem. You may not doubt their competence because you have a problem with a new unit.
They have to solve it til lit works fine and on the parts is a warranty of 3 or 5 years.
Even a new unit can fail , even it's a Mitsubishi.

We have a client who installed in November last year a PUHY200 from Mitsubishi with 4 indoor units. he had nothing but troubles with one of the indoor units (in a server room of a hospital hear nearby) since the start-up. This cassette still decreases in cooling capacity and on some days - not every day- when the client arrives in the morning, the server room is at more then 33°C. Since more then 3 months now, 3 movable splits are installed in this room together with the cassette, regulated at 28°C, in case of.

Mitsubishi Belgium came now already 3 times to the site. They always bring with them their 'very handy portable computer' with their very specialized 'maintenance software tool' They connect it to the system and log for some days all the values.

Manifolds??? They don't need it anymore, all with the computer. The modern techs of these days!!!

First conclusion: there were electrical interferences, noises on the lines, caused by the fact that no shielded wires where used for the control wires.
They also cutted away some wired bridges on the PCB.
OK, rewired everything with shielded wires. Was a big job for my client.

OK, connected the computer again and logged again for a week. In the meantime, indoor unit decreased slowly in capacity some times during this logged week.

They saw this time that the R407c was even not fractioned. Wow, they can even see each component of the gas, without a spectrometer. What are these Japanese engineers such a smart guys.

But what they saw was that there was a gas in the system which didn't belonged in there: nitrogen or air.
But, LP and HP were normal, alle the logged temperatures were within the specs.
Again, I felt stupid I'm that old fashioned guy who does everything with the manifold, temperature meter and a sliding ruler of Danfoss.

OK, evacuated all the R407c, vacuumed till 2 Torr for almost 2 days and refilled it with new gas. They even can calculate with a computer how many gas there gas to be filled in a system.
17.6 kg, wow,...17.6,.. not 17.8 or 17.4 no 17.6 . Again,...wow, what a smart Japanese engineers. They even don't need a sight glass and they even don't need a liquid receiver. Both should of course be very handy but who am I to doubt their competence.

And the wonder happened, the system cooled.
For 2 days.

Computer is now connected again on the system. I wonder what the magical software now will say.

I also asked also the engineer the following because the system was running at 18 bar in cooling mode for an ambient temperature that day of +/-15°C. "Why not lower the HP to increase capacity, increase COP and decrease power consumption?" They use EEV's, so this is perfect possible.

The answer was predictable: "Well, the software" again the magical software "determines the right HP and we can't change this. But it can't harm the system if it runs at that pressure"
I stopped asking questions.
It can't harm indeed the system but it should harm less our environment if it should run with a lower HP.

There was also no satisfying answer why there was a swing of +/- 0.75 bar on the LP while measuring. If we install a pack, the PLC holds the LP on 4.25 bar, not 4.30 and not 4.20,...4.25 bar.
Why can't they just do this simple regulation?

I told you this story just to say:
1. it's not because something happens that we made a fault.
2. it's not because there are a lot of electronics in the units that these units are de facto better units.
3. It's not because you can connect a computer to a system that these systems can serviced better, faster and more accurate.
4. It's not because you call a specialised engineer that they can pinpoint the problem. Replacing PCB's, well my youngest son of 13 can co this.
5. If you can't apply the thermodynamic basics to a systems , even if the space the PCB's and the contollers takes is larger then then condenser, even if you can connect 15 computers to the system, you will not solve the problem.

These conclusions can also be made for EEV's in a refrigeration system.

They better had replaced the whole indoor unit like we asked the first time.

Coming back to your questions: 33 bar =55°C condensing and 10 bar = 11°C evaporating.
Seems both very, very high. Air in the system perhaps?
They better should restart completely

[frank]

Should have fitted a Daikin

[Swedish AC]

Thanks for that, i agree that the system is under all the warranties but the unit is installed by a sub contractor to Mitsu and when the engineer cant answer my simple questions and has to refer back to Mitsu then i started to wonder myself if they knew what they were doing 100%. So with no "evidence" that the system is malfunctioning due to my lack of knowledge then i can only tell them that it will not cool the rooms enough. I have not given up hop tho and i will keep on at thm till im satisfied, they will get bored of me calling all th etime and finally help i hope.

If the installation is new and was done by the official importer of Mitsubishi, all should be done under warranty of the techs who installed these units, so why worry before.
Same for the pipe sizes, that's their problem. You may not doubt their competence because you have a problem with a new unit.
They have to solve it til lit works fine and on the parts is a warranty of 3 or 5 years.
Even a new unit can fail , even it's a Mitsubishi.

We have a client who installed in November last year a PUHY200 from Mitsubishi with 4 indoor units. he had nothing but troubles with one of the indoor units (in a server room of a hospital hear nearby) since the start-up. This cassette still decreases in cooling capacity and on some days - not every day- when the client arrives in the morning, the server room is at more then 33°C. Since more then 3 months now, 3 movable splits are installed in this room together with the cassette, regulated at 28°C, in case of.

Mitsubishi Belgium came now already 3 times to the site. They always bring with them their 'very handy portable computer' with their very specialized 'maintenance software tool' They connect it to the system and log for some days all the values.

Manifolds??? They don't need it anymore, all with the computer. The modern techs of these days!!!

First conclusion: there were electrical interferences, noises on the lines, caused by the fact that no shielded wires where used for the control wires.
They also cutted away some wired bridges on the PCB.
OK, rewired everything with shielded wires. Was a big job for my client.

OK, connected the computer again and logged again for a week. In the meantime, indoor unit decreased slowly in capacity some times during this logged week.

They saw this time that the R407c was even not fractioned. Wow, they can even see each component of the gas, without a spectrometer. What are these Japanese engineers such a smart guys.

But what they saw was that there was a gas in the system which didn't belonged in there: nitrogen or air.
But, LP and HP were normal, alle the logged temperatures were within the specs.
Again, I felt stupid I'm that old fashioned guy who does everything with the manifold, temperature meter and a sliding ruler of Danfoss.

OK, evacuated all the R407c, vacuumed till 2 Torr for almost 2 days and refilled it with new gas. They even can calculate with a computer how many gas there gas to be filled in a system.
17.6 kg, wow,...17.6,.. not 17.8 or 17.4 no 17.6 . Again,...wow, what a smart Japanese engineers. They even don't need a sight glass and they even don't need a liquid receiver. Both should of course be very handy but who am I to doubt their competence.

And the wonder happened, the system cooled.
For 2 days.

Computer is now connected again on the system. I wonder what the magical software now will say.

I also asked also the engineer the following because the system was running at 18 bar in cooling mode for an ambient temperature that day of +/-15°C. "Why not lower the HP to increase capacity, increase COP and decrease power consumption?" They use EEV's, so this is perfect possible.

The answer was predictable: "Well, the software" again the magical software "determines the right HP and we can't change this. But it can't harm the system if it runs at that pressure"
I stopped asking questions.
It can't harm indeed the system but it should harm less our environment if it should run with a lower HP.

There was also no satisfying answer why there was a swing of +/- 0.75 bar on the LP while measuring. If we install a pack, the PLC holds the LP on 4.25 bar, not 4.30 and not 4.20,...4.25 bar.
Why can't they just do this simple regulation?

I told you this story just to say:
1. it's not because something happens that we made a fault.
2. it's not because there are a lot of electronics in the units that these units are de facto better units.
3. It's not because you can connect a computer to a system that these systems can serviced better, faster and more accurate.
4. It's not because you call a specialised engineer that they can pinpoint the problem. Replacing PCB's, well my youngest son of 13 can co this.
5. If you can't apply the thermodynamic basics to a systems , even if the space the PCB's and the contollers takes is larger then then condenser, even if you can connect 15 computers to the system, you will not solve the problem.

These conclusions can also be made for EEV's in a refrigeration system.

They better had replaced the whole indoor unit like we asked the first time.

Coming back to your questions: 33 bar =55°C condensing and 10 bar = 11°C evaporating.
Seems both very, very high. Air in the system perhaps?
They better should restart completely

[Makeit go Right]

How big is your conservatory and did it get warm/hot before the aircon unit was installed? I can guess that Sweden is not as warm as some places, but a Conservatory in strong sunlight should get reasonably warm.

It would surprise me if 2.5kW would do more than tickle it. I do not know the size or the aspect in relation to the sun, etc, but I would be surprised it anything less that 5kW will do the job in a conservatory. In some small ones with not much sun, maybe a 3.5kW would do, but 2.5kW?